From 14bfb0aca4160d8323760ccb8d77f0bbc37fc0a3 Mon Sep 17 00:00:00 2001
From: Daniel Chappuis <chappuis.daniel@gmail.com>
Date: Mon, 17 Oct 2016 22:41:33 +0200
Subject: [PATCH] Some optimizations in contact solver

---
 src/collision/ContactManifold.h |  6 ++--
 src/engine/ContactSolver.h      | 58 ++++++++++++---------------------
 2 files changed, 23 insertions(+), 41 deletions(-)

diff --git a/src/collision/ContactManifold.h b/src/collision/ContactManifold.h
index 2f77e9b2..c36c1476 100644
--- a/src/collision/ContactManifold.h
+++ b/src/collision/ContactManifold.h
@@ -102,7 +102,7 @@ class ContactManifold {
         short int mNormalDirectionId;
 
         /// Number of contacts in the cache
-        uint mNbContactPoints;
+        int8 mNbContactPoints;
 
         /// First friction vector of the contact manifold
         Vector3 mFrictionVector1;
@@ -187,7 +187,7 @@ class ContactManifold {
         void clear();
 
         /// Return the number of contact points in the manifold
-        uint getNbContactPoints() const;
+        int8 getNbContactPoints() const;
 
         /// Return the first friction vector at the center of the contact manifold
         const Vector3& getFrictionVector1() const;
@@ -264,7 +264,7 @@ inline short int ContactManifold::getNormalDirectionId() const {
 }
 
 // Return the number of contact points in the manifold
-inline uint ContactManifold::getNbContactPoints() const {
+inline int8 ContactManifold::getNbContactPoints() const {
     return mNbContactPoints;
 }
 
diff --git a/src/engine/ContactSolver.h b/src/engine/ContactSolver.h
index becd5529..089d8b53 100644
--- a/src/engine/ContactSolver.h
+++ b/src/engine/ContactSolver.h
@@ -119,11 +119,8 @@ class ContactSolver {
          */
         struct ContactPointSolver {
 
-            /// Accumulated normal impulse
-            decimal penetrationImpulse;
-
-            /// Accumulated split impulse for penetration correction
-            decimal penetrationSplitImpulse;
+            /// Pointer to the external contact
+            ContactPoint* externalContact;
 
             /// Normal vector of the contact
             Vector3 normal;
@@ -134,41 +131,26 @@ class ContactSolver {
             /// Vector from the body 2 center to the contact point
             Vector3 r2;
 
-            /// Cross product of r1 with 1st friction vector
-            Vector3 r1CrossT1;
-
-            /// Cross product of r1 with 2nd friction vector
-            Vector3 r1CrossT2;
-
-            /// Cross product of r2 with 1st friction vector
-            Vector3 r2CrossT1;
-
-            /// Cross product of r2 with 2nd friction vector
-            Vector3 r2CrossT2;
-
-            /// Cross product of r1 with the contact normal
-            Vector3 r1CrossN;
-
-            /// Cross product of r2 with the contact normal
-            Vector3 r2CrossN;
-
             /// Penetration depth
             decimal penetrationDepth;
 
             /// Velocity restitution bias
             decimal restitutionBias;
 
+            /// Accumulated normal impulse
+            decimal penetrationImpulse;
+
+            /// Accumulated split impulse for penetration correction
+            decimal penetrationSplitImpulse;
+
             /// Inverse of the matrix K for the penenetration
             decimal inversePenetrationMass;
 
-            /// Inverse of the matrix K for the 1st friction
-            decimal inverseFriction1Mass;
+            /// Cross product of r1 with the contact normal
+            Vector3 r1CrossN;
 
-            /// Inverse of the matrix K for the 2nd friction
-            decimal inverseFriction2Mass;
-
-            /// Pointer to the external contact
-            ContactPoint* externalContact;
+            /// Cross product of r2 with the contact normal
+            Vector3 r2CrossN;
 
             /// True if the contact was existing last time step
             bool isRestingContact;
@@ -181,11 +163,14 @@ class ContactSolver {
          */
         struct ContactManifoldSolver {
 
+            /// Pointer to the external contact manifold
+            ContactManifold* externalContactManifold;
+
             /// Index of body 1 in the constraint solver
-            uint indexBody1;
+            int32 indexBody1;
 
             /// Index of body 2 in the constraint solver
-            uint indexBody2;
+            int32 indexBody2;
 
             /// Inverse of the mass of body 1
             decimal massInverseBody1;
@@ -199,18 +184,12 @@ class ContactSolver {
             /// Inverse inertia tensor of body 2
             Matrix3x3 inverseInertiaTensorBody2;
 
-            /// Number of contact points
-            short int nbContacts;
-
             /// Mix friction coefficient for the two bodies
             decimal frictionCoefficient;
 
             /// Rolling resistance factor between the two bodies
             decimal rollingResistanceFactor;
 
-            /// Pointer to the external contact manifold
-            ContactManifold* externalContactManifold;
-
             // - Variables used when friction constraints are apply at the center of the manifold-//
 
             /// Average normal vector of the contact manifold
@@ -275,6 +254,9 @@ class ContactSolver {
 
             /// Rolling resistance impulse
             Vector3 rollingResistanceImpulse;
+
+            /// Number of contact points
+            int8 nbContacts;
         };
 
         // -------------------- Constants --------------------- //